Circuit arrangement and method for verifying a switching diversity system

ABSTRACT

In a circuit arrangement and method for testing a radio receiving system, the circuit arrangement includes multiple antennas, an antenna selector switch for the antennas, a receiver, and a diversity processor that controls the antenna selector switch. A diagnostic processor has an output terminal connected to a control input of the diversity processor, which provides at its output terminal, a signal that prevents the diversity processor from performing any further switching operations.

FIELD OF THE INVENTION

The present invention relates to a circuit arrangement and a method fortesting a diversity switching system.

BACKGROUND INFORMATION

Diversity antenna switching systems are described, for example, inEuropean Published Patent Application No. 0 201 977. The system isessentially a single component having antenna switches and a TEA6101diversity processor with a TDA1596 IF demodulator, both from Philips.The diversity processor detects receiving disturbances by evaluating anIF signal supplied from the radio, subsequently using the antenna switchto switch over to another antenna, the signal quality of which, in turn,is tested, etc.

This system does not make it possible to easily activate specificantennas for testing, i.e., to connect them to the radio input terminal.

A circuit arrangement that achieves this object is described in GermanPublished Patent Application No. 195 13 872. The following is adescription of this circuit arrangement, with reference to FIG. 1.Switching between (for example) four antennas 1, 2, 3 and 4 isaccomplished by providing an antenna switch 5, which is controlled by adiversity processor 6. Control signals which are generated by ademodulator 10, and which demodulator 10 derives from the IF signalprovided by a receiver (radio) 8 having one or more speakers 9, arepresent at diversity processor 6.

A converter 51, which is controlled by a control unit, e.g., radio 8, isprovided to continuously activate specific antennas. To do this, thecontrol unit generates a digital signal that is transmitted to converter51, for example, via the antenna cable with separating filter 52, or viathe IF line used to control the diversity system. Converter 51 useselectronic switches to select one of, for example, four antennas 1, 2, 3or 4. However, because diversity processor 6 is not deactivated duringtesting of the selected antenna, its switching pulses may interfere withthe incoming signal.

The procedure described in German Published Patent Application No. 19513 872 has the advantage that it is relatively easy to implement.Nevertheless, it has the disadvantage that it can test only the functionof the antennas, but not the function of the diversity processor itself,and the diversity processor remains in operation while the function ofan antenna is being tested.

The express reference made to the above-mentioned publications and tothe product description of the above-mentioned circuits also applies toall details and technical objects not described in greater detail here.

SUMMARY

It is an object of the present invention to provide a circuitarrangement and a method for testing a diversity switching system thatmay be used to test not only the function of the antennas, but also thatof the diversity processor itself.

In particular, the circuit arrangement according to the presentinvention prevents the processor from generating, during diagnosis,switching signals that interfere with the function test.

According to the present invention, a diagnostic processor is provided,which has an output terminal connected to a control input of thediversity processor and which provides, at its output terminal, a signalthat prevents the diversity processor from performing any furtherswitching operations.

In particular, use may be made of a characteristic of conventionaldiversity processors, such as the Philips TEA6101 circuit. Thisdiversity processor may, for example, interrupt switching to anotherantenna when a stop signal is supplied to its control input.

The diagnostic processor provided according to the present inventiongenerates the stop signal at the exact moment when it determines thatthe selected antenna has been activated by the diversity processor.Diagnosis is not accomplished by using an additional control unit forthe antenna switch, according to the present invention, but rather thediversity processor is suitably controlled so that it continuouslyactivates the selected antenna independently of the antenna signal atthe moment.

For clarity, it should be noted that the use of the term “processor”does not imply that this circuit needs to be a microprocessor ormicrocontroller. “Hard-wired” circuits may also be used instead ofprocessors of this type.

The circuit arrangement according to the present invention may be used,for example, to perform diagnosis as follows:

1. A frequency at which a relatively weak signal is received is firstset at the radio. This is necessary because the diversity processorswitches to the antenna only within the receiving level range at whichnoise may be heard in the speaker.

2. The number of the antenna to be set is entered at the radio eithersubsequently or beforehand. The radio transmits this value to thediagnostic processor.

3. Existing receiving signal fluctuations, or fluctuations that areproduced, for example, by touching the antenna, cause the diversityprocessor to switch to another antenna. If the diagnostic processordetermines that the desired antenna is set using a comparator, forexample it sets the stop signal for the diversity processor. Theachievement of this state is transmitted back to the radio and displayedthere.

4. Switching to another antenna is an indication that the diversityprocessor is in proper working order. The antenna itself may then betested, for example, by performing an audio test.

If a more thorough test of the system is necessary, for example forfinal inspection during manufacturing, conventional test signals may beused to test both the diversity switching threshold and the antennafunction.

The directional characteristics of the individual antennas may also betested by disconnecting the antenna cable from the radio input andsupplying the antenna output signal to a measuring receiver.

According to a further example embodiment, it is possible to use specialswitching actions to cause the system to switch to the next antennaduring diagnosis. This may be accomplished, for example, by brieflydeactivating all antennas and thereby triggering switchover by thediversity processor. This action is most easily performed directly atthe antenna switch at the concentration point of the switching diodes.

It is also possible to use the demodulator level signal to evaluate theantenna receiving level more precisely. In the range relevant fordiversity operation, the magnitude of this signal is largelyproportional to the receiving level and may therefore be compared to areference signal during the test.

According to a further example embodiment, a test unit producedspecifically for the intended purpose may be used instead of the radioas the control unit for the diagnostic processor.

Without limiting its scope and nature, the present invention isdescribed below, by way of example, on the basis of embodiments withreference to the drawing, to which express reference is made for thepurpose of describing all details according to the present inventionthat are not explained in greater detail in the text.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a four-antenna diversity system withdiagnostic function according to the related art.

FIG. 2 is a schematic view of an example embodiment of a four-antennadiversity system according to the present invention, having a diagnosticfunction.

FIG. 3a is a schematic view of a first example embodiment of adiagnostic processor according to the present invention.

FIG. 3b is a schematic view of a second example embodiment of adiagnostic processor having the ability to deactivate all antennassimultaneously.

FIG. 3c is a schematic view of a third example embodiment of adiagnostic processor having the ability to evaluated the IF signallevel.

FIG. 3d is a schematic view of a further example embodiment of thediagnostic processor with the ability to deactivate all antennassimultaneously and to evaluate the IF signal level.

FIG. 4 is a schematic view of an example embodiment of an antenna switchwith the ability to deactivate all antennas simultaneously.

FIG. 5 is a schematic view of a four-antenna diversity system withdiagnostic function and transmission of the test signals over the IFline.

DETAILED DESCRIPTION

In the Figures, the same reference numbers always refer to the sameparts, making it unnecessary to introduce these parts repeatedly in theexplanation of further figures.

FIG. 2 is a block diagram of an example embodiment of an antennadiversity system having diagnostic function. Four antennas 1 through 4are connected to an antenna switch 5, which is controlled by a diversityprocessor 6 and which “switches” the signal of a particular antenna toits output terminal according to the control function. The output signalof antenna switch 5 present at this output terminal (RF signal) issupplied to a radio 8 having at least one speaker 9, which may be used,among other things, to perform an acoustic evaluation.

According to the present invention, a diagnostic processor 7 isprovided, the function of which is described below.

Diagnostic processor 7 has input terminals for the four switching lines(in the example embodiment illustrated) for antenna switch 5, oneinput/output terminal for the digital test signals and one further(optional) input terminal, the function of which is explained below.

The IF signal generated by receiver 8 is supplied to a demodulator 10over a coaxial cable. Demodulator 10 internally generates, from the IFsignal, the level and audio signals, which are sent to diversityprocessor 6. The level signal, which is also supplied to the other inputterminal of diagnostic processor 7, is a DC signal proportional to theIF signal level and enables the receiving level to be evaluated. Theaudio signal is the modulation content of the radio signal.

Diagnostic processor 7 may also have an output terminal at which ispresent a signal that may be used to deactivate all antennas.

The operation of diagnostic processor 7 provided according to thepresent invention is explained in greater detail below with reference toFIGS. 3a to 3 d. The same reference numbers refer to the same parts asin FIG. 2 and do not need to be described again.

FIG. 3a illustrates a first example embodiment of diagnostic processor7:

The four antenna switching lines (in the example embodiment illustrated)are routed to a comparing element 71. The comparison input terminals ofcomparing element 71 are connected to a register 72 which stores thenumber of antenna 1, 2, 3 or 4 to be set for the diagnosis. The numberof the antenna is transmitted from radio 8 to comparison input terminalsof register 72 via an interface 73. Interface 73 also provides adiagnosis enabling signal, which, together with the output signal ofcomparing element 71, is present at an AND element 74 in the form of aninput signal, the output signal of which is present, in the form of astop signal, at the control input terminal of diversity processor 6.

FIG. 3b illustrates a modification of the example embodiment illustratedin FIG. 3a, in which interface 73 has an output terminal at which asignal is present which may be used to deactivate all antennas 1 . . .4. This feature, which may be used when switching to the next antenna,must not or may not be triggered by a poor-quality incoming signal, butrather exclusively by the control unit at a specific point in time.

According to the example embodiment illustrated in FIG. 3c, not only thetest signals generated by radio 8, but also the output signal of awindow comparator 75, which compares the level signal to a referencevoltage U_(ref), is present at the interface. This characteristic may beused to test the diversity system in the automobile manufacturer'sfacilities during vehicle production, using defined frequency-modulatedRF test signals.

FIG. 3d illustrates an example embodiment that has the samecharacteristics as the example embodiments illustrated in FIGS. 3b and 3c.

It is possible to extend the illustrated circuit to more or fewer thanfour antennas at any time.

FIG. 4 illustrates an example embodiment of an antenna switch 5, whichenables all antennas to be deactivated simultaneously. Without limitingthe overall configuration, illustrated antenna switch 5 has two inputs53 and 54 that are connected to a radio output terminal 57 as a functionof switching signals present at terminals 55 and 56. Reference number 58identifies a deactivation input terminal. When a control signal withzero potential is present at terminal 58, circuit point 59 becomesconnected to plus voltage +Ub due to the deactivated transistor, so thatthe switching diodes may no longer conduct current, and a signal is nolonger present at terminal 57. This arrangement makes it possible todeactivate all antennas with a single signal.

FIG. 5 illustrates a modification of the example embodiment illustratedin FIG. 2, in which the test signals are routed via the IF cable tosimplify the wiring. This arrangement enables the two diplexers on,,theradio and processor sides, of which only diplexer 710 on the processorside is illustrated in FIG. 5, to couple in and out. The diplexer on theradio side is not illustrated because it is located inside the radio. Itis not practical to use the RF antenna cable for this purpose becausethe latter may need to be removed from the radio, for example, tomeasure the antenna directional diagrams. The antenna cable is thenconnected to a measuring receiver. If it is still necessary to controlthe antenna or activate a particular antenna under these circumstances,the control signals may be transmitted from the radio to the diversitycircuit over a cable other than the RF signal cable.

What is claimed is:
 1. A circuit arrangement for testing a radioreceiving system, comprising: multiple antennas; an antenna selectorswitch for the antennas; a receiver; a diversity processor configured tocontrol the antenna selector switch; and a diagnostic processorincluding an output terminal connected to a control input of thediversity processor and providing, at its output terminal, a signalconfigured to prevent the diversity processor from performing furtherswitching operations, and wherein the diagnostic processor furtherincludes a comparing element, at which signals of antenna selectorswitching lines and output signals of a register are present, the outputsignals of the register indicating a number of the antenna to be set fordiagnosis.
 2. The circuit arrangement according to claim 1, wherein thediagnostic processor provides the signal that prevents further switchingoperations when the diversity processor has switched to a specific,preselectable antenna.
 3. The circuit arrangement according to claim 2,wherein the diagnostic processor includes input terminals at whichswitching signals of the diversity processor for the antenna selectorswitch are present.
 4. The circuit arrangement according to claim 2,wherein the receiver sends to the diagnostic processor a signal used toselect a specific antenna.
 5. The circuit arrangement according to claim4, wherein a number of the selected antenna is enterable at thereceiver.
 6. The circuit arrangement according to claim 1, wherein thereceiver is configured to transmit test signals along with a diagnosisenabling signal.
 7. The circuit arrangement according to claim 6,wherein the test signal includes the number of the antenna.
 8. Thecircuit arrangement according to claim 6, further comprising an IF cableconfigured to route the test signals, two diplexers arranged on areceiver side and a diagnostic processor side providing coupling in andcoupling out.
 9. A method for testing a radio receiving system includingmultiple antennas, an antenna selector switch for the antennas, areceiver and a diversity processor configured to control the antennaselector switch, comprising the steps of: setting a frequency at which arelatively weak signal is received at the receiver; selecting a specificantenna; switching over the antennas by the diversity processor;preventing the diversity processor from performing further switchingoperations as soon as the diversity processor has performed theswitching over step; displaying the switchover to the specific antenna;and testing a diversity switching threshold and an antenna function inaccordance with known test signals.
 10. The method according to claim 9,wherein the diversity processor is caused to perform the switching overstep in accordance with one of an existing incoming signal fluctuationand a fluctuation produced by touching the antenna.
 11. The methodaccording to claim 9, wherein the testing step includes the substeps oftesting directional characteristics of individual antennas by switchingto the antenna to be tested, subsequently disconnecting an antenna cablefrom a receiver input and connecting the antenna cable to a measuringreceiver.
 12. The method according to claim 9, further comprising thesteps of: providing a demodulator with an IF signal generated by thereceiver; generating a level signal from the IF signal by thedemodulator; comparing a magnitude of the IF signal to a reverencesignal to provide more precise evaluation of an antenna receiving level,the magnitude of the IF signal substantially proportional to thereceiving level in a relevant range for diversity operation.
 13. Themethod according to claim 9, wherein the receiver includes a test unitused as a control unit for a diagnostic processor.
 14. A method fortesting a radio receiving system including multiple antennas, an antennaselector switch for the antennas, a receiver and a diversity processorconfigured to control the antenna selector switch, comprising the stepsof: setting a frequency at which a relatively weak signal is received atthe receiver; selecting a specific antenna; switching over the antennasby the diversity processor, wherein the switching over step includes thesubstep of switching over to a next antenna by briefly deactivating allof the antennas directly at the antenna selector switch at aconcentration point of a switching diode; preventing the diversityprocessor from performing further switching operations as soon as thediversity processor has performed the switching over step; anddisplaying the switchover to the specific antenna.